29 Sep 2011

Confidence

Throughout our school years, our teachers keep asking us to be humble. In medical school, we are taught not to jump to conclusions. We should always consider differential diagnoses and perform more confirmatory tests.

Have we followed their advice? Is the advice sound?

Let’s consider the second question first. In the last issue of Nature, Dominic Johnson and James Fowler used an evolutionary model to show that overconfidence confers survival advantage. [Nature 2011;477:317-20] When more than one person competes for resources, the decision to fight depends on the chance of winning as well as the cost of losing. If each person has perfect knowledge on the strength of oneself and the other competitors, the decision is straightforward. You only claim the resources when you are stronger than others, and should not fight at all in face of a stronger opponent.

In reality, however, perfect knowledge is rare. The decision is therefore based on an estimation of one’s strength in relation to others. As a result, a person who overestimates his strength would fight more often than average, while one who underestimates oneself would more likely give up. According to Johnson’s and Fowler’s model, overconfident populations would claim more resources in most situations and gradually grow in strength. The only exception is when the cost of losing is particularly harsh. For example, when KL was a senior medical officer, you would be a fool to argue with him about call duties. First, you still lose the argument. Second, he gives you an extra call next month.

No wonder we see so many arrogant people around. Now that we understand how they evolved, we should no longer hate them but congratulate them for improving our species. In an accompanying commentary, van Veelen and Nowak named a number of real life examples. [Nature 2011;477:282-3]

"Most people report their driving abilities to be above average. 70 percent of high school students think their academic performance is above average. 94 percent of professors rate their teaching abilities as above average."

I can easily add more items to the list. 100 percent of endoscopists underestimate their average cecal intubation time. 95 percent also overestimate the size of peptic ulcers they treated and polyps they removed. Don’t be surprised if you read an endoscopy report saying there was a 5 cm ulcer in the narrow first part of duodenum.

That is why we are so competitive.

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